The invention relates to an apparatus which substantially eliminates the risk of interrupting or destroying an electrical circuit by external electro-static discharge through a switch. Any electrical circuit that operates at low voltage, such as one in computer systems, faces a risk of damage or interruption by accidental introduction of high-voltage electro-static discharge through a switch. Many computer systems operate under 12 volts, while external electro-static discharge by a human operator may be up to 15000 volts. An introduction of such high voltage to an electric circuit often takes place when a human operator with static charge touches a switch of the electric device. Although such static discharge is instantaneous, sufficiently high voltage rushes through the switch and reaches the internal circuit. As a result, the operation of the internal circuit is interrupted, and the circuit may be destroyed.
In the relevant prior art, an electrical circuit is protected by a grounded chassis. In U.S. Pat. No. 4,868,702 a plurality of circuit blocks are protected by the ground circuit apparatus which includes the grounded chassis. Such chassis physically separates an internal circuit from the external electro-static discharge. Some semiconductor devices are also protected by the built-in overvoltage protection mechanism such as in U.S. Pat. No. 4,809,044.
In protecting the circuit from electro-static discharge by personnel, U.S. Pat. No. 4,800,374 teaches the use of a wrist anti-static device. Assembly workers or repairmen wear this device to ground themselves to prevent a damage to the circuit due to electro-static discharge. It is not practical for end-users to wear such device every time that they operate an electrical device.
In every day-operation, a switch is a portion of an electrical system where an undesirable external high voltage is introduced. Although a switch is often mounted on the grounded chassis, high voltage due to electro-static discharge on the surface of switch is not directly shielded to ground. Thus, the relevant prior art does not address the problem of high voltage introduced to the surface of the switch in protecting the internal electric circuit.